The invention relates to a silencer with a shunt resonator.
From the publication xe2x80x9cIntake Silencing of Commercial Vehiclesxe2x80x9d, Lothar Bending, ATZ, Apr. 4, 1978, it is already known that, at a silencer in the intake duct of an internal combustion engine, a particular longitudinal piece can be surrounded by an outer housing. In a region of the housing cover, the intake duct is partially perforated, as a result of which a volume formed between the intake duct and the outer housing is coupled acoustically.
It is therefore an object of the invention to construct a silencer of the type mentioned above in such a manner that the silencing behavior of the silencer can be calculated and influenced as a function of the sound frequency.
The silencer of the present invention is advantageously suitable to accomplish at least this objective by way of the features as described and claimed hereinafter. Since the acoustically effective openings in the intake duct comprise pipe elements which extend from the intake duct into the housing volume of the shunt resonator, it is possible to exert a positive effect on the silencing behavior by suitably dimensioning and arranging the pipe elements.
The modifiable pipe elements form openings in the intake duct which advantageously allow the shunt resonator, also referred to as a Helmholtz resonator, to be tuned simply for silencing even low frequencies.
The volume of the shunt resonator is defined by an annular space between the intake duct and the outer housing with the formation of an acoustic neck by the pipe elements assuming a position of prime importance. The number and position of the pipe elements as well as their length and their diameter are advantageously selected in such a manner that their acoustic silencing gains develop in a specified frequency range.
In order to also advantageously utilize so-called breaking-in frequencies with silencing losses on either side of the resonance frequency, the position of the pipe element in relation to the center of the shunt resonator can be shifted in the longitudinal direction in such a manner that the silencing losses are shifted by interaction with further components surrounding the silencer into frequency ranges at which the silencing losses are not disturbed. In the most advantageous case, this can lead to a silencing gain.
In the case of a particularly advantageous embodiment, the sound-carrying channel is the intake duct for the intake air of an internal combustion engine and the sound emissions, which are to be silenced, are produced by the intake pulses of the individual cylinders, especially of a diesel engine.
The silencer of the present invention can be produced in an advantageous manner owing to the fact that the region having the pipe elements in the sound-carrying channel is an injection molded part that can be inserted between two ends in the intake duct and that the enveloping housing volume of the shunt resonator formed by housing halves are mounted at each end of the duct and the two halves of the housing can be joined together permanently, enclosing the injection molded part.
In order to form the pipe elements with a simple design, the pipe elements can also be produced separately and attached and extrusion coated individually during the production of the injection-molded part.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.